1. Field of the Invention
The present invention concerns an electrochromic mirror comprising a glass substrate, a transparent conductive film formed on the back of the glass substrate, an electrochromic layer formed on the back of the transparent conductive film and a reflection and electrode film formed on the back of the electrochromic layer.
2. Statement of Related Art
The electrochromic mirrors described above are used, for example, as anti-dazzling mirror for vehicles and disclosed, for example, in Japanese Patent Unexamined Publication (JP-A) No. 2000-2895.
By the way, the electrochromic layer is constituted with an electrolyte film, and an oxidation color forming film and a reduction color forming film putting the electrolyte film therebetween, in which ions transfer in the electrochromic layer due to hydrolysis of a trace amount of water content present in the electrolyte film to cause change between coloration and color extinction.
For example, in a case where the oxidation color forming film is an IrOn film, an electrolyte film is a Ta2O5 film, and a reduction color forming film is a WO3 film, the following chemical changes are taken place upon color extinction and coloration in the oxidation color forming film, the electrolyte film and the reduction color forming film.
[Upon Color Extinction]                Oxidation color forming film; Ir(OH)n+xOH−        Electrolyte film; Ta2O5+xH2O        Reduction color forming film; WO3+xH++xe−        
[Upon Coloration]                Oxidation color forming film; Ir(OH)n+x+xe−        Electrolyte film; Ta2O5+xH+xOH−        Reduction color forming film; HxWO3         
When a potential difference is provided between the transparent conductive film and the reflection and electrode film, electron e− starts transfer at the electrodes on the side of the respective color forming films and a trace amount of water in the electrolyte is hydrolyzed by the energy of transfer to cause transfer of ions and, as a result, oxidation/reduction reaction is taken place in each of the color forming films to cause coloration and color extinction.
By the way, in each of the color forming films, positive ions (H+) are attracted each other and such positive ions (H+) result in repetitive oxidation and reduction. However, in a case where positive ions such as Na+ are intruded to form, for example, NaOH or like other compound, ion conductivity in the film is lowered and the repetitive reaction occurs no more. Since various ions are present in atmospheric air and, among all, Na+ ions are present in a great amount, it is necessary to shut the intrusion of ions from the outside into the electrochromic layer.
In JP-A No. 2000-2895 described above, the electrochromic layer is covered and protected with a resin film having ion shielding property, water proofness, moisture proofness and scratch resistance together for stabilizing the performance of the electrochromic mirror.
However, it is difficult to completely shield the ions by the resin film described above and, while the resin film is incorporated with metal oxides, ceramic powder and glass powder in the prior art, it is still difficult to completely shield the ions. In addition, since the method of forming the electrochromic layer and the method of forming the resin film are different from each other, this deteriorates the productivity.